A printing operation generates printed material by applying ink to a type of substrate using any of a variety of different methods. In large printing operations, the operation may be used to produce a large amount of printed material. For example, in rotogravure printing presses, a substrate such as a web of paper or film is sequentially driven through a series of engraved cylinders, each using ink of a different color, which cooperate to imprint a multicolor image on the web. Using this method, each cylinder has its own supply of a single color of ink. The amount of ink that is used for each cylinder is usually different from any other cylinder and is dependent on the image being applied to the web, the thickness of the ink, the coverage level, etc. Tracking ink usage and availability is important since a printing operation relies on having constant availability of a variety of different colors of inks that are often used in differing amounts and/or at differing rates.
Printing operations rely on having availability of ink having a consistent color and other characteristics to produce printed material with a correct and consistent appearance. During a print operation, adjustments to the formulation of an ink may be necessary in order to maintain this correct and consistent appearance. For example, it may be determined that a small amount of red pigment or extender (unpigmented ink) should be added. However, in order to calculate how much of an ingredient to add, it is important to know not only the characteristics of the ink being added to a reservoir and the ink already in the reservoir, but also the amount of ink remaining in the reservoir and in the system at any given time.
In some systems for ink measurement, ink levels in the reservoirs may be monitored by metering devices in the ink lines and/or by scales monitoring the weight or mass of the reservoir holding the ink. For example, the weight monitoring method includes determining the amount of ink that has been used by successive weighing of the ink reservoir. This method has also been used in combination with pump stroke measurement, a type of metering device, to refine the ink level calculation.
However, both methods have known drawbacks. For example, metering devices may not be usable in certain types of printing methods such a rotogravure printing press where the ink is constantly recirculated and applied by immersion of the engraved cylinder rather than pumped. Further, meters may be inaccurate since a number of different factors can cause actual ink consumption to vary from meter measurement values. The factors can include the variability of the volume of ink displaced with each pump stroke and backflow of the ink in the pump. These depend on the specific gravity, viscosity and tackiness of the ink as well as the age and wear of the pump. A number of these problems can be avoided by using ink weighing to determine the amount of ink in a reservoir, but this method requires additional steps such as scale calibration, scale maintenance, methods for recognizing outlier weightings, such as during a filling/exchange operation, etc. A weighing operation may further cause unavailability of the reservoir during weighing. Further, both metering devices and ink weighing scales are additional components that must be purchased, maintained and upgraded, increasing the cost of the printing operation.
Accordingly, it is desirable to provide a system and method for monitoring the consumption of ink without utilizing metering devices and/or ink weighing. What is further needed is such a system and method configured to facilitate color correction calculations based on the monitored ink consumption.